Method of producing rimmed steel ingots and chilling cap therefor



Jan. 10, 1939. G A DOW 2,143,410

METHOD OF PRODUCING RIMMED STEEL INGOTS AND CHILLING CAP THEREFOR Filed April 9, 1957 J7 .0", INVENTOR v G eo rge A.Dor'nin M 444 9 flhmb.

Patented Jan. 10, 1939 UNITED STATES PATENT OFFICE lHETHOD OF PRODUCING RIMIVIED STEEL INGOTS AND CHILLING CAP THEREFOR 9 Claims.

This invention relates to the production of rimmed steel ingots, and more particularly to a method of cappingrimmed steel ingots in order to produce ingots which are denser than those produced in accordance with the prior practice of capping.

In the accompanying drawing which illustrates, by way of example only, certain preferred em bodiments of the present invention,

Figure 1 is a vertical longitudinal section through a mold and ingot which is to be capped in accordance with the present invention, the view illustrating the shape of the ingot and rim at the time that the chilling cap is to be applied;

Figure 2 is a view similar to Figure 1, but il lustrating the chilling cap applied to the ingot; and

Figures 3 through 6 illustrate different embodiments of chilling caps which may be employed in accordance with the present invention.

In the production of rimmed steel ingots, the steel is poured into the ingot molds with the carbon-iron oxide reaction incomplete. When this metal is chilled by coming in contact with the surface of the mold, the reaction referred to is activated and this produces quite a violent evolution of gases. These gasesform bubbles in the mold mainly in planes parallel to the side walls of the mold. Being lighter than the metal, they tend to rise and, in rising, cause currents in the metal, the currents being indicated by arrows on Figure 1. It is well known that steel always tends to solidify by the formation of crystals called dendrites, these forming at right angles to the surface chilled and growing inwardly. The currents in the molten metal washing across the tips of these crystals prevent their inward growth and result in a series of layers similar to the skin of an onion. It is this difference in type of crystallization that helps give to rimmed steel one of its valuable characteristics, namely, ability to stand deep drawing. In accomplishing this, however, it is necessary to produce considerable excess of gas to create the currents necessary to produce proper rimming. As the boiling action continues, a ring or rim of solidified metal forms around the periphery of the ingot at its upper end and at this time the level of the top surface of the molten metal drops below the level of the top of the rim. If nothing further were done, the growth of this rim would continue until it closed the major portion of the top surface of the ingot. At this stage, a major part of the metal has now solidified and the still molten interior has, because of loss of temperature, become pasty. The gases still forming within this molten mass are no longer able to rise therein and have a tendency to puff up the pasty interior into a spongy mass. Due to this pulling up effect, the

level of the top of the still molten interior now rises and is likely to overflow the top of the rim. It has a tendency to form a volcano-like crater which is commonly called a nigger head.

It is the common practice at the present time 'to prevent this spewing out and formation of nigger heads by applying to the ingot a flat chilling cap. This cap rests on the upper surface of the rim of the ingot. The pufiing up of the plastic metal continues until the mass rises to the level of the upper edge of the rim when it contacts with the chilling cap which forms a crust on the metal, which crust prevents or decreases the further formation of gases within the body of the steel. It will be seen, however, that in the -prior practice, the liberation of gases continues during that period while the molten mass is rising into contact with the lower surface of the chilling cap. Since the metal is in a plastic state during its rise, the gases formed do not readily escape and a large portion at least of the gases is trapped in thesteel, puffing it up and forming gas bubbles commonly called blow holes.

In accordance with the present invention, I cause a crust to form on the molten mass while the molten metal is at a level below the level of the top of the rim, rather than waiting for the steel to become plastic and rise to the level of the top of the rim. This results in an ingot which is much freer from blow holes than can be produced in accordance with prior practices, for the reasons hereinafter pointed out.

Referring now to Figure 1, the steel has beenpoured into a mold I and has solidified along the sides and bottom of the mold, as indicated by the dotted line 8. A rim 9 has formed on the steel, but the steel it! within the rim still remains fluid. Accordingly, the bubbles which are formed and which travel in the upwardly pointing portions of the paths indicated generally by the reference numeral 1 I are able to, and do, escape from the fluid metal rather than. being trapped therein, as would be the case if the metal were in its plastic state. I then apply a cap l2, as shown in Figure 2, in order to form a crust on the flu d metal 10 while it is below the level of the rim. Due to the building up of pressure, this prevents the further formation of gas bubbles which would result in blow holes in the metal. In this way, the formation of the blow holes is largely prevented and is compensated for by the formation of a small pipe I3, as shown in Figure 2. It is seen, therefore, that by the present method those gases which would be formed and which would result inthe production of blow holes in the ingot, if the plastic metal was allowed to rise from the level III to the level 25 of Figure 1, is prevented or largely decreased. Ingots produced in accordance with the present invention, therefore, are considerably denser and freer from blow holes than those produced in accordance with prior known methods.

Figures 3 through 6 illustrate different forms of caps which may be used in accordance with the present invention. In each of these embodiments the caps are made out of metal such as steel or other good heat conducting medium, so that when the cap is applied to the molten metal in the ingot mold, it will rapidly conduct away heat and form a crust thereon. The cap illustratedin Figure 3 comprises a plate or flanged portion l5 adapted to rest on the rim of theingot and a downwardly extending portion I6 adapted to extend below the rim of the ingot. The downwardly projecting portion IS in this embodiment is convex.

The cap illustrated in Figure 4 comprises a plate or flanged portion l1 and a concavo-convex downwardly projecting portion [8 forming a ring. The cap illustrated in Figure 5' comprises a plate l9 and a plurality of downwardly projecting knobs or convex portions 20. Each of the caps illustrated in Figures 3, 4 and 5 may be made as castings. The cap illustrated in Figure 6 is cup or basin shaped and may be made from pressed metal. It comprisesa rim 2| and a convex bottom portion 22 connected by a flanged portion 23. The flange 23 is adapted to rest on the rim of the ingot and the portion 22 to extend downwardly below the rim. Water or other cooling fluid may be introduced into the cap so as to aid in cooling the metal.

In the standard method of capping a five ton ingot, the cap is placed on the rim about minutes from the time the mold is filled and it takes about 5 minutes more for the steel to puff up until the metal touches the cap, creating the crust necessary to stop reaction. During this 5 minutes, serious blow holes, amounting to about 1% of the total volume of the ingot, form therein. Under the preferred operation of my method, I place the cap approximately 5 minutes after the mold is filled, and as the crust forms instantly, no blow holes form in the ingot after the placing of the cap. A further advantage of this early capping made possible by my method is that I cut the time during which motion and curents are prevalent in the molten mass from approximately minutes to approximately 5 minutes and thereby decrease the tendency to, and the degree of, segregation. Segregation is fundamentally the result of motion and is prevented or lessened by quiet.

The volume of the downwardly extending portion 06 of the cap l5 shown in Figure 3, or the corresponding parts in Figures 4, 5 and 6, is.pref erably substantially equal to the volume within the rim of the ingot between the level of the top surface III of the molten mass at the time of capping and the horizontal plane of the top of the rim. This volume, bounded by the surface III, the plane 25 and the inner periphery of the rim 9, is designated in Figure 1 by the reference letter A. The volume of the portion IQ of the cap illustrated in Figure 3 is preferably (of cooling fluids, such for example as water or cold air.

Although I have illustrated several embodiments of the invention and have described in detail the preferred manner of practicing the invention, it is to be understood that the invention may be otherwise embodied or practiced within the scope of the following claims.

I claim:

1. A method of producing rimmed steel ingots in which an ingot rim is formed adjacent the upper end of the ingot, comprising pouring metal in a mold, causing a boil of the metal, producing a rim of solidified metal around the periphery of the upper end of the ingot above the level of the still molten portion of the ingot, and positively solidifying a crust on the molten metal while it is at a level in the mold below the top of the solidified rim, the crust being sufliciently strong to prevent material increase in the volume of the ingot during further solidification.

2. In a method of producing rimmed steel ingots in which an ingot rim is formed adjacent the upper end of the ingot, the step comprising causing a crust to form on the molten metal below the level of the top of the ingot rim, the crust being sufficiently strong to prevent material increase of the volume of the ingot thereafter.

3. In a method of producing rimmed steel ingots, the step comprising causing a crust to form on the molten metal when the levelof the molten metal is at substantially its lowest point below the level of the top of the ingot rim, the crust being sufficiently strong to prevent material increase in the volume of the ingot during further solidification 4. In a method of producing rimmed steel ingots, in which an ingot rim is formed adjacent the upper end of the ingot, the step comprising contacting the metal within and below the ingot rim with a chilling cap.

5. In a method of producing rimmed steel in gots, in which an ingot rim is formed adjacent the upper end of the ingot, the step comprising contacting the metal within and below the ingot rim with a chilling cap while supporting the cap from the ingot rim.

6. A metallic chilling cap adapted for producing rimmed steel ingots, the cap having a portion adapted to rest on the rim of the ingot and a portion extending downwardly therefrom within the rim.

- "I. A metallic chilling cap adapted for producing rimmed steel ingots, the cap having a portion adapted to rest on the rim of the ingot and a portion extending downwardly therefrom within the rim, the volume of the downwardly extending portion of the cap being equal to a substantial portion of the volume within the rim and between the level of the top surface of the molten metal at the time of capping and the horizontal plane of the top of the rim.

8. A metallic chilling cap adapted for producing rimmed steel ingots, the cap having a portion adapted to rest on the rim of the ingot and a portion extending downwardly therefrom within the rim, the volume of the downwardly extending portion of the cap being substantially equal to the volume within the rim and between the level of the top surface of the molten metal at the time of capping and the horizontal plane of the top of the rim,

9. A metallic chilling cap adapted for producing rimmed steel ingots, the cap having a. portion adapted to rest on the rim of the ingot and a downwardly extending portion within the rim forming a ring.

GEORGE A. DORNIN.

CERTIFICATE OF CORRECTION Patent No. -2,1L ,u1o. January 10,- 19 9;

GEORGE A. DORNIN.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 2, second column, lines 7 and 8, claim ,1, strike out the words "in which an ingot rim is formed adjacent the upper end of the ingotf' and insert the same after the syllable "gots and before the comma, line 25, claim 5; and that the said Letters Patent shouldbe read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 21st day of February, A', D. 1959.

Henry Van Arsdale (Seal) Acting Commissioner of Patents. 

